/*******************************************************************************
* SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU Lesser General Public License Version 2.1 or later (the
* "LGPL"), in which case the provisions of the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of the LGPL, and not to allow others to use your version of
* this file under the terms of the EPL, indicate your decision by deleting
* the provisions above and replace them with the notice and other provisions
* required by the LGPL. If you do not delete the provisions above, a recipient
* may use your version of this file under the terms of the EPL or the LGPL.
* 
* Based on the original MiniSat specification from:
* 
* An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
* Sixth International Conference on Theory and Applications of Satisfiability
* Testing, LNCS 2919, pp 502-518, 2003.
*
* See www.minisat.se for the original solver in C++.
* 
*******************************************************************************/
package org.sat4j.minisat.core;

import java.io.Serializable;


/**
 * The responsibility of that class is to choose the phase (positive or negative)
 * of the variable that was selected by the IOrder.
 * 
 * @author leberre
 *
 */
public interface IPhaseSelectionStrategy extends Serializable {
   
    /**
     * To be called when the activity of a literal changed.
     * 
     * @param p
     *            a literal. The associated variable will be updated.
     */
    void updateVar(int p);

    /**
     * that method has the responsibility to initialize all arrays in the
     * heuristics. 
     * @param nlength the number of variables managed by the heuristics.
     */
    void init(int nlength);
    
    /**
     * initialize the phase of a given variable to the given value.
     * That method is suppose to be called AFTER init(int).
     * 
     * @param var a variable
     * @param p it's initial phase
     */
    void init(int var, int p);
    
    /**
     * indicate that a literal has been satisfied.
     * 
     * @param p
     */
    void assignLiteral(int p);
    
    /**
     * selects the phase of the variable according to a phase
     * selection strategy.
     * 
     * @param var a variable chosen by the heuristics
     * @return either var or not var, depending of the selection strategy.
     * 
     */
    int select(int var);
}
